Properties and Applications of Nilcra® Zirconia PSZ

Similar to the creation of Wi-Fi (wireless internet), the origins of Partially Stabilized Zirconia (PSZ) is a commercial success story that emerged from research performed at Australia’s CSIRO. The first patent on PSZ technology was awarded in 1978 (US Patent 4,067,745) to researchers Hannink, Pascoe, and Garvie.

The paper published in the journal Nature in 1975 by Garvie, Hannink, and Pascoe, titled “Ceramic Steel” is one of the most crucial events in the history of PSZ.

This paper described the transformative toughening phenomena that is the cause of PSZ’s incredible mechanical features, specifically fracture toughness and strength (Modulus of Rupture).

Referring to several physico-chemical properties shared between alloy systems in the iron and zirconia systems, they suggested that PSZ could be known as the ceramic analog of TRIP steel.

In 1979, an Australian company called Nilsen Sintered Products first obtained sole rights to the technology. Under the trade name Nilcra® Zirconia, the production of PSZ happens in Melbourne to the present day, the company having been bought by Morgan Advanced Materials plc (UK) in 2008.

The History of Nilcra® Zirconia in Australia

  • 1975   CSIRO advertises PSZ license
  • 1979   Nilsen Sintered Products Pty Ltd, Separation Street, Northcote, obtained the license for the individual international manufacture of PSZ
  • 1980   Delivery of first production furnace
  • 1981   Nilsen (USA) Inc. created in Elmhurst, Chicago to market and promote PSZ in North America
  • 1984   Nilcra® Ceramics Pty Ltd was founded by a joint venture between CRA Limited and Nilsen
  • 1984   A new dedicated plant was constructed, comprising development facilities and a new laboratory at the NSP Northcote site
  • 1988   ICI Australia Pty Ltd obtained Nilcra® and also bought alumina components business R&W in Auburn, California, USA, becoming ICI Ceramics Inc. new North American sales and marketing office
  • 1990   ICI Advanced Ceramics relocated to exclusive facilities in Redwood Drive, Notting Hill
  • 1991   European sales office launched in Bracknell, UK
  • 1997   Carpenter Technology Inc., USA obtained ICI Advanced Ceramics and founded ‘Carpenter Advanced Ceramics Pty Ltd’ as a wholly owned subsidiary
  • 2008   The Morgan Crucible Company plc, UK obtained company and founded ‘Morgan Technical Ceramics Australia Pty Ltd’ as a wholly owned subsidiary

Zirconia Engineering Ceramics

Zirconia is an engineering ceramic existing in three main crystalline forms according to temperature:

properties and applications of nilcra zirconia psz

The disruptive phase transformation from tetragonal to monoclinic that happens throughout cooling is of specific interest.

This phase change is brought in with a 3 to 5% volume expansion, which is harmful when manufacturing high-purity zirconia ceramics as it creates cracking that extensively compromises the mechanical integrity of the end product.

The production of a completely stabilized zirconia ceramic material that comprises entirely of the cubic phase is possible.

Advanced research into zirconia ceramics has discovered that ideal mechanical features are made when the multi-phase PSZ material is created. This material comprises the cubic phase with a slight dispersion of tetragonal, nano-sized precipitates.

The composition of Nilcra® Zirconia PSZ can be attained through stabilizing agents and sufficient heat treatment being introduced. The tetragonal phase is metastable and will change to monoclinic when put under external stresses such as diamond grinding.

High levels of stress generated at stress concentrations, or micro-flaws in the material, make the tetragonal phase transform locally into the monoclinic phase.

As previously stated, there is a corresponding volumetric expansion that generates compressional closing stress on any crack fronts that stop crack propagation. This consequently creates a ‘transformation toughening’ influence that results in fracture toughness and very high strength (MOR).

Common stabilizing agents are cubic oxides, for example, CaO, MgO, Y2O3 and CeO2. The additions of stabilizing agents are relatively small, while commercial formulations are kept secret and optimized. In the example of MgO, CSIRO data suggests a further level of 3 mol.% to create the greatest rupture strength.

Properties of Nilcra® Zirconia PSZ

Many engineering ceramics fit the requirements when imagining a material that is incredibly hard and resistant to wear and can function at high temperatures and in corrosive environments.

If an engineering ceramic needed to remain in good condition after continued blows with a sledgehammer, then PSZ would likely be the ideal candidate.

Check out the video at to see the material in action. It is an engineering ceramic like no other.

PSZ is characterized by the following features:

  • Exceptional toughness and strength
  • High hardness
  • High fracture toughness
  • Very good resistance to corrosion
  • Chemically inert, making it adequate for use in challenging environments
  • Very good abrasion, wear resistance, and erosion
  • Electrically insulating
  • Non-magnetic
  • Thermal expansion coefficient like steel
  • Low thermal conductivity

This mixture of features has seen PSZ replace more conventional materials, for example, tungsten carbides, hardened steels, and metal alloys, particularly in applications requiring high levels of corrosion and wear resistance.

Applications

The excellent chemical and mechanical characteristics of Nilcra® Zirconia sees it function effectively in a wide range of challenging service industries as far-reaching as mining and minerals processing, cement, pulp and paper, food and battery production, power generation, and metal forming.

It is also frequently utilized in a range of process valves and pump components, including ball and butterfly valves, liners, seats, plugs, discs, sleeves, plungers, and cages. It is suitable for use in difficult bearing applications such as bearings for pumps, chemical digestion tanks, and screw conveyors.

Nilcra® Zirconia tooling is additionally employed in the steel canning industry for seaming and spin flange rollers and in different applications for metal forming, for example, calendering rollers for copper wire drawing and extrusion dies.

The material can also be applied in the directional drilling of tool components employed in oil and gas exploration and fuel injectors for diesel engines. Components created from PSZ can reduce corrosion and wear and offers the advantages of less downtime, lower maintenance costs, and an extended life span.

Summary

Nilcra® Zirconia has rightfully earned the title of ‘Ceramic Steel’ despite the term seeming contradictory.

With its extraordinary mixture of features mostly generated by the transformation toughening mechanism, Nilcra® Zirconia is a high-performance engineering ceramic that can function in challenging service conditions.

It will continue to discover applications where it outperforms specialty alloys and steels.

For wear and corrosion issues, conversion from metal to Nilcra® Zirconia will assist users with extensive benefits in product performance, decreased downtime, and prolonged service life.

Acknowledgments

Produced from materials originally authored by Dr. Cameron Chai and Martin Stuart from Morgan Technical Ceramics.

This information has been sourced, reviewed and adapted from materials provided by Morgan Advanced Materials - Technical Ceramics.

For more information on this source, please visit Morgan Advanced Materials - Technical Ceramics.

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